Traffic supervisory system



July 13, 1965 J. BARKER TRAFFIC SUPERVISORY SYSTEM 6 Sheets-Sheet 2Filed May 13, 1957 INVENTOR.

JOHN L. BARKER lmaxdz ATTORNEY July 13, 1965 Filed May 13, 1957 J. L.BARKER TRAFFIC SUPERVISORY SYSTEM MAKE BEFORE BREAK TIMING.

/ 4 bun- /CHARGING VOLTAGE CHARGING VOLTAGE \CUT- OFF. ya

REFERENCE POTENTIAL (GNDJ 6 Sheets-Sheet 4 INVENTOR. JOHN L BARKER ATTORNEY July 13, 1965 J. L. BARKER TRAFFIC surmwrsomr sYs'rEM 6 Sheets-Sheet6 Filed May 13, 1957 United States Patent 3,195,126 TRAFFIC SUPERVKSORYSYSTEM John L. Barker, Nor-walk, Conn, assignor, by mesne assignments,to Laboratory for Electronics, Inc., Boston, Mass, a corporation ofDelaware Filed May 13, 1957, Ser. No. 658,704 8 Claims. (Cl. 3437) Thisinvention relates to a system for remote or centralized recording and/orindicating of the speed and/or volume of moving traffic such as vehicleson a traffic pathway, and in particular to means for obtaining andrecording or indicating for specific and/ or average intervals of timethe trafiic volume and speed of a single or group of highway facilitiesat one or more sampling points or spaced intervals along suchfacilities. The term hig way facilities is intended to include withoutlimitation highways, parliways, throughways, turnpikes and other heavilytravelled traffic facilities for example.

Highway facilities designed for particular vehicular speeds and trafficvolumes may under certain conditions become inadequate so that meanshave to eventually be provided for alleviating the inadequacy, either byincreased highway personnel, or by modifying and/ or adding new highwayfacilities. To provide for the advance planning of such proposedfacilities, means are required to maintain proper and continuous recordsof the performance of the facility. Such records may be in the form ofvisual observations which, of necessity, require substantially largepersonnel to adequately cover the facilities. This form of recordkeeping would be costly and subject to error because of the humanelement involved.

Further, it is necessary at times to have an immediate spot check of anygiven facility at various stations to determine the traffic conditionsthereat and to take any necessary steps to alleviate any irregularconditions which may exist at the particular station. This againrequires increased personnel to maintain strict vigilance in assuringthat normal highway conditions will not be disturbed.

According to a preferred aspect of the invention as contemplated herein,there is provided a plurality of spaced sampling stations along a givenhighway facility, each sampling station being provided with means forsampling trafiic speed and trailic volume, and for developing signalinformation indicative of said volume and speed, such information thenbeing relayed to a remote or centralized monitoring station forrecording or indication there.

According to a further aspect of the invention such speed and Volumeindicative signal information is derived at one or more such samplingstations and is then combined and transmitted via common transmissionfacilities to a central monitoring station where the said combinedsignal information is received and separated according to theaforementioned volume and speed indicative signal information. The speedand volume signals are then processed by speed and volume indicatorunits and preferably recorded graphically for permanent viewing.

According to other aspects of the invention centralized speedinformation from spaced sampling points along a highway facility mayhave significant application without the volume information. Anotherfeature of the invention resides in providing alarm facilities, at thecentral monitoring station, adapted to provide audible and/or visualsignal means responsive to speeds or average tralfic volumes whichexceed or fall below set predetermined levels.

It is, therefore, an object of this invention to provide "ice animproved type traffic surveillance or supervisory or monitoring systemfor highway facilities.

It is another object of this invention to provide apparatus at spacedsampling stations along a highway facility for detecting the presenceand speed of vehicles moving along said highway facility.

A still further object of this invention is to provide apparatus at oneor more sampling stations along a highway facility for combiningreceived traffic information indicative of speed and volume at thesampling station and transmitting such information along a predeterminedtransmission path to a central monitoring station where the saidinformation is monitored.

And a still further object of this invention is to provide, in a tratlicsurveillance system, a plurality of trailic sampling stations havingtraffic speed and/ or volume detecting means and a central monitoringstation therefor, said monitoring station having a lesser number oftraffic volume and/or speed indicators and/ or recorders selectivelyconnectible to various individual such speed and/ or volume of movingvehicles past the sampling stations selected for surveillance, and tographically record such information indicative of speed and volume forpre-determined periods of time.

Another object of this invention is to provide, in a tramc surveillancesystem, alarm circuitry operably re sponsive to excessive or low speeds,and/ or high or low volume.

Further objects, features and advantages of the present invention willbecome apparent by references to the fo lowing description taken inconjunction with the following drawings wherein:

FIG. 1 shows a typical traiiic sampling remote monitor station andapparatus for receiving tramc information indicative of the trafficspeed and tratlic volume.

FIG. 2 shows a plurality of spaced sampling stations disposed along ahighway facility and a central monitoring station for receivingindividually traihc information from the sampling stations withassociated alarm indicators. 7

FIG. 2a shows alarm circuitry for use with FIG. 2.

FIG. 3 shows a central monitoring station with selective switchingapparatus for selectively associating individual monitor and recordingequipment with individual sampling stations.

FIG. 4a shows a speed sensing detector and FIG. 4b a speed translator,both in block form, for obtaining speed information of passing vehicles.

FIG. 5a shows in block form two units of one form of volume sensingdetector for obtaining signal information indicative of the number ofpassing vehicles in any given interval of time.

16. 5b shows circuitry comprising a composite mixer for producing acomposite signal from signal information received from both volume andspeed sensing detectors.

FIG. 6 illustrates graphically the wave forms of the signals produced bythe volume detector apparatus and the speed detector apparatus and thecomposite mixer.

FIG. 7 shows circuitry for resolving, i.e. separating the speed andvolume signals from the received composite transmitted signal.

FIG. 8a shows schematically a pair of detector impulse input circuitsand a volume computer providing an output voltage proportional toaverage volume as determined by the rate of such impulses, as receivedfrom the volume output of the resolver of FIG. 7.

PEG. 8b shows according to one form of the invention, circuitry forclassifying volume information by dividing the output voltage scale intoadjustable segments or output levels in accordance with traffic volume,said levels being positively and rapidly switched in one level at a timeaccording to the trai'fic volume.

FIG. 9 shows graphically the volume graduated levels or segments overthe over-all scale with no overlapping of segments or levels.

Referring now to FIG. 1, there is shown in block form a trafhcsurveillance or monitoring system taken at a generally typical locationalong a highway facility where the tral'iic prevailing is sampled as tospeed and volume, and the information indicative thereof transmitted toa remote monitoring station.

The highway facility is shown by upper and lower horizontal lines P11and P2 representing the two edges of a roadway P for vehicular traflic.For the purpose of showing one form of applying the invention to aroadway carrying one-way two lane vehicular trafiic, the lane line CL ofthe roadway is shown by the broken line along the middle of the roadwayand a pair of cars C1 and C2 are shown traversing the highway in thesame general direction from the left side of the figure and proceedingto the right side as shown by the arrows D1 and D2 in the dual lanes oneither side of the highway lane line CL.

This illustrates one half of a typical four lane divided highway, whichmay include throughway or parkway, for example.

A pair of volume sensing detectors l and Z are each generally disposedover and above the respective dual lanes a distance of the order of 16to 18 feet for example to secure the best traflic coverage. The volumesensing detectors It and 2 are each positioned, and adapted to transmitmicrowave energy and receive such energy refiected from passingvehicles, such received wave energy being detected and converted toappropriate signals adapted for convenient transmission over normalcommunication channels.

The volume sensing detectors 1 and 2, as contemplated in the presentinvention, and shown in block form in PEG. a, each substantiallycomprises a combined radio frequency oscillator and detector 3 fortransmitting and receiving microwave energy via a microwave antenna 4,and thereby producing a Doppler beat frequency 5 in the output of theoscillator-detector 3 in response to the passage of motor vehicles alongthe highway facility. As a vehicle approaches the volume sensingdetector, the angle between the vehicles direction of travel and anyincident radio wave from the transmitter is relatively small, giving aDoppler beat of nearly true value corresponding to the speed of thevehicle, i.e., a relatively high frequency. A low pass filter s isprovided, which reduces the zone of response operation. Since a vehiclepassing under the unit at any speed is subject to the reduction offrequency of the Doppler beat note, due to the cosine effect or theangle between the direction of movement of the vehicle and the directionof transmission of the radio waves, to essentially zero, the length oftime that the Doppler beat note is reduced to a value which will bepassed by the amplifier 7 is roughly inversely proportional to the speedof the vehicle.

T1 e result is that the volume sensing detectors 1 and 2 will produce arelatively long impulse for a slowmoving vehicle and a relatively shortimpulse for a fastmoving vehicle, the pulse starting at the time whenthe vehicle enters into the corresponding effective zone of thetransmission beam and ending when the vehicle leaves such eliectivezone.

FIG. 6 illustrates the pulse wave forms 8 and 9 for a pair of vehiclesmoving in the same general direction, starting at times t1 and t2 whenthe respective vehicles come into the zones of the beams and ending attimes t3 and :4 when the respective vehicles move out of the zones ofthe beams. it can be appreciated that wave forms 3 and 9 commence atdifferent times indicating that the vehicles come into the zones atdifferent times. Any error produced by the vehicles coming into the beamlzone coincidentally, one distinguishable wave form being produced as aresult, would be rather small and insignificant in view of the remotepossibility that two vehicles would be completely aligned at the beamfronts at the same time.

The resulting wave forms 3 and 9, produced by the volume sensingdetectors, are then transmitted to a pair of detector relays RA and RB,shown in FIG. 5b. The relays RA and RB as shown in FIG. 5b are locatedpreferably with and forming a part of the composite mixer 24, the saidmixer to be subsequently described. The location as to the relays may bealtered, e.g. the relays may be located within the volume sensingdetectors to form a part thereof as illustrated by the block D.C. relayin FIG. 5a.

The relays RA and RB, are of the make-before break type and operable onDC. pulses produced by the volume sensing detectors in the wave forms 8and 9 shown in FIG. 6. Since the impulses from a pair of volume sensingdetectors might overlap by an appreciable amount, as above stated, whencars are in the zones of both units at the same time, and thus give asingle output impulse if the circuits are directly connected inparallel, means are provided for elimination of this source of error.This is accomplished through the make-before break contacts on relays RAand RB. Actuation of relay RA provides a short interval of closure ofcontact 10 to 12 during the movement of such contact, and discharges acharged capacitor 13 through 14 to ground 15. The operation of themake-before-break contact gives two impulses for each single operationof either IRA or RB; namely, an impulse When the relay is energized andanother impulse When the relay is deenergized. These impulses cause thecontacts ltl and 12 of relays RA and RB to connect the capacitor 13 toground.

FIG. 5b further shows one preferred form of blocking oscillator 30,comprising dual triode stages 31 and 32 each having respectively anodes33, 34, grids 35, 36 and cathodes 3'7, 38. The triode stages are eachrespectively coupled via capacitor 39 from anode 34 to grid 35 and viathe cathodes 37, 33. The frequency of oscillation of the oscillator isdetermined by the tuned circuit 49.

In operation, the oscillator is blocked (no conduction in the anode 34)by virtue of the high positive bias placed on the cathode 38 produced bythe charged capacitor 13. Upon the discharge of capacitor 13 to a sourceof reference potential, namely ground, through resistance 14, theoscillator 30 becomes operative, thereby producing in the output 39a, aseries of oscillations whose frequency is dependent upon the tunedcircuit 40, and preferably of the order of 2000 cycles. Asaforementioned, the discharge of capacitor 13 in accordance withimpulses from the volume sensing detectors, which cause relay RA and RBto function respectively, will render the blocked oscillator operativeto produce a series of oscillations whose duration is dependent upon thetime constant of the capacitor 13 and the plate resistance of theoscillator 30, and preferably of the order of 16 milliseconds forexample.

The 2000 cycle signal is then transmitted to a mixing stage 56. Themixer of composite mixer 24, comprises a pair of triodes in a singleenvelope wherein the anodes 51, 52 and cathodes 53, 54 are connectedtogether and the control grids 55, 56 are independent of each other. Thesignals to be mixed, or added, are transmitted separately to theindependent control grids 55, 56 and added in the plate or anode circuit57 of the mixer.

As previously described, the volume detector impulses 8 and 9 eachproduces two bursts of 2000 cycle oscillations, one at the leading edgest1 and t2, and another at the trailing edges t3 and t4 as illustrated inwave forms x1 and x2 respectively in FIG. 6. The burst for each impulselasts for a period dependent upon the time constant of the capacitor 13recharging circuit. Representative curves yi and y2 of FIG. 6 shows thecharge and discharge curves for capacitor 13 and the point of cut-offfor the oscillator stage. Curves x1 and x2 each depicts the burst andits duration for the period of time where the capacitor voltage is lessthan cut-off, with the tubes oscillating, as shown by the capacitordischarge-charge curves yl and y2.

Referring to FIGS. 1 and 4a-4a there is shown a speed sensing detector20, for measuring the speed of objects moving along a substantiallypredetermined path, and similar to the speed meter described in my US.Letters Patent No. 2,629,865 issued to Eastern Industries, Inc, assigneeof John L. Barker, on February 24, 1953. The speed sensing detectorcomprises essentially a combination transmitter-receiver unit having anoscillator 21 and mixer 22 and an antenna 23 for beaming microwave radiofrequencies at advancing or receding vehicles in the operating zone andreceiving the same frequency back plus or minus a Doppler frequencyshift. The Doppler frequency signal 23a is then amplified bypre-amplifier 23b and subsequently transmitted via a composite mixer 24,to a remote monitoring station, where it is ultimately processed into adirect speed reading.

The said Doppler signal may also be processed directly at the pointwhere the Doppler frequency was developed. In the case where the Dopplerspeed signal 23a is transmitted to the composite mixer 24, the signal23a is first fed to the control grid 56 of mixer 50 and ultimately mixedin the anode circuit 57 with the aforementioned representative 2000cycle signal produced from the volume detector sensing signals. TheDoppler speed signal is an audible signal, i.e. in the range from 0 to730 cycles for example, which corresponds approximately to a vehicletravelling at the speed of from 0 to 100 miles per hour. The variableaudible signal 23a, having a variable frequency from approximately 0 to730 cycles, is then combined with the 2000 cycle signal as abovementioned in the mixer anode circuit 57, which circuit further includesa transformer 58. The transformer output 59, when both speed and volumesensing detectors are operated in response to the presence of vehiculartrafiic, contains both the volume representative 2000 cycle signal andthe speed representative 0-730 cycle signal, the respective signals bothforming a single composite signal 60, which is subsequently transmittedvia some available transmission means. The transmission means can takeon any of the normal available forms such as telephone lines and/ orradio transmission links.

The composite signal 60, containing both traffic volume information andtraflic speed information is subsequently transmitted via appropriatetransmission facilities to a remote sampling station monitor 70. FIG. 1shows in elemental block form the essential equipment for handling bothvolume and speed vehicular trafiic information received from somerepresentative trafiic sampling station. The resolver 71 is essentiallya frequency separation device which receives the transmitted compositesignal 60 comprised of both volume and speed frequency information andseparates the said volume and speed frequency information into theirseparate frequencies, e.g. 2000 cycles and 0-730 cycles respectively.

With reference to the composite signal 60, one form of such signal isillustrated in the wave forms W1 and W2 of FIG. 6. Either W1 or W2 willrepresent a single vehicle, and W1 and W2 as shown may represent closelyspaced vehicles with partially overlapping speed signals, which whileshown separately for clearness, would actually be consolidated by simpleaddition of the voltage waves as well known into a single composite waveform.

The short volume signal bursts in W1 and W2 correspond with those of X1and X2, and the long low frequency wave trains at the right in W1 and W2illustrate the Doppler speed frequency signal tapering off in amplitudeas the vehicle recedes in the beam. While these volume and speed signalsare shown separated in W1 and W2, it will be appreciated that their timerelation will depend on the spacing of the volume sensing and speedsensing detectors. In practical operation the volume signals areseparable from the speed signals by the resolver even when overlapping.

The speed signals will actually include a lower frequency initialportion as the vehicle enters the near edge BB1 of the beam due to thecosine effect and this aids in distinguishing partially overlappingspeed signals since this introduces a significant dip in or during theconsolidated speed signal from partly overlapping signals W1 and W2 forexample.

The edges BEl-BEZ of the radio beam may represent half-power pointsindicating that the major portion of the energy is within these lines,but some energy extends outside sufficient to produce in most cases areadable low frequency initial part of the speed signal.

The beam BE1-BE2 may be angled more or less to the roadway than shown inFIG. 1 to meet individual conditions.

More specifically, as shown in FIG. 7, the resolver comprises a pair ofinput terminals 72 and 73 connected to an input transformer 74 whosesecondary 75 feeds the input stage of an amplifier 76 via apotentiometer 77. A second amplifier 78 has also its input stage fed bythe transformer secondary via a coupling resistor 79. Thus the compositesignal 60, having both volume and speed representative frequencies, isfed via transformer 74 to both input stages of amplifiers 76 and 78respectively. The input filter 80 to amplifier 78 comprises a tunedparallel LC circuit, tuned to a resonant frequency of 2000 cycles, sothat only that portion of the composite signal 60 having a frequency ofapproximately 2000 cycles will be extracted therefrom and transmitted tothe amplifier 78 via grid 81 and amplified. The composite signal 60 fedto amplifier 76 via grid 82 is amplified and transmitted through a pietype low-pass filter network 180 whose pass-band extends fromapproximately zero to 1000 cycles. Therefore, essentially allfrequencies above 1000 cycles are cut-off, assuring that no volumesensingfrequencies of approximately 2000 cycles are passed ortransmitted here.

The 2000 cycle volume signal, after amplification by amplifier '78, isthen transmitted to a detector 82a to provide a D.C. operating voltagefor relay stage 83. The detected output of the 2000 cycle burst signal,indicative of the presence of vehicles, is shown in pulse form in FIG. 6curves Z1 and Z2. The DC. voltage or pulse amplitude necessary to causerelay stage 83 to conduct sufiiciently, to permit the operation of relay84 in anode circuit 85, is dependent upon the bias placed on the stage83 via threshold control variable resistor 86 as applied to the cathode87 of stage 83. The operation of relay 84, in accordance with thepresence of 2000 cycle volume sensing signals, closes contacts 88 andprovides the repeated detector impulse at the said contacts and atoutput 88a, for operation of the volume measuring equipment, whichequipment comprises separately the volume translator 90, volumeindicator 91 and volume recorder 92.

Referring to FIG. 8a there is shown a pair of input circuits 94 and 95which are each adapted to function with the output relay circuit 83a ofFIG. 7. The operation of relay 84 closes contacts 88 to complete anexternal circuit of the type illustrated in FIG. 8a. For purposes ofillustration there is shown in FIG. 7 only a single resolver having onlya single detector output, the said output feeding only one of the inputcircuits of FIG. 811. However, where there are a number of samplingstations provided for the purpose of acquiring traflic data over aconsiderable expanse of highway facilities, if desired to provide anaverage volume from two sampling stations for example, a pair ofresolvers and outputs therefrom may feed the respective input circuits94 and 95. However, if individual volume averaging or indicating isdesired for each sampling station, its resolver output will be the onlyone connected to the input of the volume 2 translator 9% at FIG. 8a andonly one input circuit will be used.

With respect to input circuit 94 for example, in absence of a vehiclevolume pulse, i.e. when contacts 88 are open, capacitor 98a will becharged from the potential divider between 13+ and ground, via thetransformer primary 99 and resistor 97 to ground. When contacts 88 closeupon a vehicle volume pulse, the capacitor 93a is discharged quickly viaresistor through the primary 99, producing a pulse through thetransformer and thus from the transformer output 100 to the pulse ratecomputer 101.

The pulse rate computer 161 is essentially a device for receiving pulsesindicative of traffic volume, i.e. pulses from individual vehicles, andcapable of converting such indicative pulses to a DC. signal whoseamplitude varies in accordance with the frequency or number of suchpulses per unit of time. The DC. signal so produced is one capable ofbeing metered by conventional voltmeters, the meter being so calibratedas to give the volume of traffic, either as a direct quantity over agiven interval of time or as some percentage of a given traffic volumeor rate of flow. A preferred type of pulse or cycle computer measuresvolume of traffic in vehicles per hour, and although not limitedthereto, is disclosed in the Manual for Electro-Matic Electronic CycleComputer, Model MC-ll, copyright 1955 by Eastern Industries,Incorporated, assignee of the present application. This computer is alsothe subject of a copending patent application by me. This type ofinstrument is adapted to [receive a pair of impulses, as shown in FIG.6, curves Z1. and 2.2, each pair giving an indication of only onevehicle. In other words, two pulses or actuations are equal to onevehicle. However, it can be appreciated that two impulses are notnecessary where it would be suiiicient to have only one, as for exampleby using the leading edge only of the pulses 8 and 9.

Whatever system of such pulses is used, it is the function of thecomputer to convert the incoming pulses to an output voltage whichvaries as a direct function of the raflic volume. In other words thevoltage produced by the computer varies linearly with respect to thetraflic volume, and corresponds to the tratiic level as averaged overthe selected time period, which latter may be adjustable. The computeroutput voltage 1&2 is applied to a classification system to operateselectively one at a time of the six output circuits Mil-M5 shown inFIG. 8b, each of the output circuits being responsive to a given rangeof computer output voltages indicative of the corresponding range oftraffic volume.

This preferred arrangement of the output circuits is especiallyadaptable for automatic surveillance of facilities where it is desirableto know the volume level at the highway facility especially if it hadreached a critical high level or critical low levels, since alarmcircuits may be operated from the low or high output circuits or both,if desired. In addition these output circuits could be connected toelapsed time indicators to indicate the total number of operation hoursof the facility in any six preselected volume ranges.

It is desirable to have each of the volume ranges cornpletelyindependent of each other, eg. with no voltage overlap. In other words,in transferring the volume range from one level to another, it isdesirable to have the transfer occur at as close as possible to the samevalue for increasing and decreasing tratiic volumes. In order toaccomplish this fast switching action, and to avoid any lag or back lashin going from one indicated level to the next indicated level, a snapaction with essentially no differential is provided in theaforementioned output circuit switching through the combined use oftubes, relays, capacitors and resistors as will be now described.

Referring again to FIG. 811, there is shown a series of output stages A,B, C, D, E, and F, each stage representing a given volume range oftrafiic. Stage A, repre- 0 senting the lowest and initial volume rangehas no control element and is connected directly to the A.C. powersource A33 via the back contacts of the several control relays. StagesB, C, D, E and F each have associated therewith a control tube Hit, 111,112, 113 and 114 respectively, and each adapted to function inaccordance with the corresponding ranges of output voltage from thecomputer.

For purposes of brevity, only the explanation of one will be given, theother functioning in the same manner, except for the voltage levelstransmitted to each to cause the operation thereof. Stage B comprises acontrol tube ill) having a control grid 115, anode 116, and cathode 117.In the anode 116 of tube 116, there is connected a relay 118 responsiveto current flow in tube Ill to cause the operational movement of contactarm 119 from contact 129, to contact 121. Before tube 119 can conduct,the voltage lilZ from computer 101 must attain a DC. level suflicient toovercome the fixed bias potential placed on the control grid 115 viabiasing potentiometers 125, 122, 124 and 123a.

To set this operating level a general potentiometer 125, 122i, 124 isprovided to give a total range of bias voltage corresponding to thetotal voltage volume range of the output on 1&2. Across the generalpotentiometer, five individual potentiometers 1230, i231), 1230, 123d,123:: are provided to give overlapping adjustability of the respectivetransfer points between voltage ranges or volume segments A, B, C, D, Eand F.

For the A-B transfer control shown in detail as an example of all, thearm of potentiometer 123a is set to a voltage bias level correspondingto the volume level at which the A-B transfer is desired. When thepositive voltage on the line 102 is equal to or greater than thenegative voltage on the arm of potentiometer 123a, the voltage of thejunction of resistors 34.34, 137, comprising a voltage divider between102 and 123a, will go to approximately zero or slightly positive. Thisjunction is connected to the control grid 115 and this causes the tubeto pass sufiicient anode current to operate relay 118 (BR) under theseconditions, i.e. when the voltage on 162 exceeds the selected value forthe AB transfer.

Each of the stages have their control grids set at some fixed biaspotential to permit the conduction of each of the control tubes onlyafter a predetermined voltage level, indicative of the traffic volume,has been attained.

To assure rapid switching from one volume range to another, relay 11%must function with quick positive action. To enable such quick positiveaction there is provided in the control grid circuit a resistive andcapacitive network designed to assure very heavy conduction of thecontrol tube lit? at the time when the voltage level reaches the end ofA volume range and the start of the next higher volume range B. FIG. 9shows graphically the input signal voltage, or computer output voltageover the various volume ranges, represented by volume ranges A, B, C, D,E and F, and the points of transition a, b. c, d and e for each of therespective ranges at which points the relays lid, 126, 127, 128, and 129are made to function in response to heavy conduction of each of thecontrol tubes associated therewith.

In operation, with respect to stage B, the biasing voltage of the grid115 is suflicient to render the tube noncondnctive up to and includingall computer output voltages in the A range. However, when the computeroutput voltage exceeds the A-range voltage by an incremental amount,switch SWBl will operate. Switch SW31 comprises a network of resistorsand condensers in the grid control circuit for the purpose of producingat the grid at large positive signal at the transition point a. This isaccomplished as follows; when the computer output voltage and the gridbias are substantially equal, tube will commence to conduct, therebycausing relay 118 (BR) (normally tie-energized) to operate. There isasso ciated with relay 1118 another set of contacts 139 and 131 and acontact arm 132. When relay 118 is de-energized,

contact arms 119 and 132 are engageable with contacts 120 and 130respectively. When the relay however is energized, the said contact armsbecome operably engageable with contacts 121 and 131 respectively. Toprovide for fast switching, contacts 131, 132 and 130 are arranged in amake-before-break sequence. While this does not show as such on thedrawing, the adjustment is such as to produce a make-before-break.

Accordingly, when contact arm 132 and contact 131 are engageable,capacitor 135 shorts out momentarily the resistor 134, thereby producingas a result a large positive going pulse at the control grid 115; thusassuring that control tube 110 conducts heavily and relay 118 is givensufficient current to pull in positively.

Similarly when relay 118 has been energized, but the grid voltage fallsbelow the level for the relay to stay in, the contact arm 132 willengage contact 130. The capacitor 136 will then short out momentarilythe resistor 137, thereby producing at the control grid 115 a largenegative going pulse thus assuring a sharp reduction in anode current tocause the relay to drop out cleanly.

By the resulting switching of the switch circuits in each of the outputstages, there is produced at each of the control tube grids either alarge positive or negative pulse, the produced pulses thus assuring theabsolute presence or absence of relay energizing current to effect asharp transition from one volume range to the adjacent volume range.

Resistors 133 and 133 serve to discharge capacitors 135 and 136respectively when the relay BR is in the deenergized and energizedpositions respectively in preparation for switching. These resistors arelarge compared to resistors 134- and 137.

Associated with each of the output stages are a series of outputterminals 140 through 145 inclusive and a series of lights 146 through151 inclusive respectively, associated therewith. The output terminalsare each selectively connected to the A.C. power source 103 whenever aparticular relay circuit is energized to effect the operation of someexternal pieces of equipment, such as elapsed time indicators toindicate the total number of operation hours of the facility in any sixpreselected volume ranges, for example, or for recording graphically thetime in different ranges for example.

As an alternative arrangement it is obvious that elapsed time meter orevent recorders could be connected effectively to operate with therespective relays 118, 126-129 by means of additional make contacts onthe latter to provide cumulative output or recording of traflic at andbelow each level.

When relays BR through FR are de-energized an uninterrupted seriescircuit from the AC. power source 103 to the output terminal 140 isconnected by virtue of the normally closed connections of contact arms119, 161, 164, 167 and 170 to the respective contacts 120, 160, 163, 166and 169. Upon energization of relay 118 (BR), contact arm 119 disengagescontact 120 and engages contact 121, thereby disconnecting the outputterminal 141) and connecting the output terminal 141 (B) to the AC.

power source.

in a similar manner each of the remaining output terminals may either beconnected or disconnected from the AC. power source depending uponwhether the particular relay circuit associated with a particular outputterminal is either energized or de-energized, the terminals only beingconnected one at a time.

The computer voltage output 192 is also fed to indicator meter 175through a calibration resistor 176, to indicate the average volume ofthe vehicular traffic, and also to a graphic type recorder 92; forvisual recording.

Now referring again to FIG. 1, the composite signal 60, comprising bothspeed and volume vehicular trafiic information, from a typical trafiicsampling station was transmitted via appropriate transmission facilitiesto a typical remote sampling station monitor '7 0. At the monitorstation the resolver 71, as previously explained, sep- 10 arated thespeed and volume frequencies indicative of the speed and volume of thesampled traffic conditions.

Referring to FIG. 7 the composite signal is transmitted to an ampli er76 and subsequently filtered by a low pass filter circuit composed ofpie-sections with L1 and L2 as the series arms and C1, C2 and C3 as theshunting or parallel arms. The pie-section filter 1315 is designed topass all signals having frequencies below 1000 cycles, those above 1000being substantially cut-off.

Therefore, the speed Doppler beat note in the range from zero to about730 cycles will be passed by the filter and ultimately transmitted tothe speed signal processing equipment which consists of a speedtranslator 181, speed indicator 182 and speed recorder 183 at themonitor station. Speed translator 181, speed indicator 132' and speedrecorder 183 at the sampling station may be similar to the correspondingunits 1151, 182 and 133 at the remote monitor station. The units 181,132' and 133 at the sampling may be omitted if local speed indication orrecording at the sampling station is not desired. The speed translatorcan be generally of the type described in my US. Letters Patent No.2,629,865 issued to Eastern Industries, Incorporated as assignee or inthe Manual for Electro-Matic Radar Speed Meter, Models S2 and S-2Aissued and copyright 1955 by Eastern Industries, Inc., which latter formof speed meter is the subject of a copending application by me. i

More specifically, and referring to FIG. 4b, the speed Doppler beat note23a emanating from the speed sensing detector 20 is transmitted toamplifier 184 where the 0-730 cycle speed signal is amplified, thenlimited by amplitude limiter 185. To assure that sufiicientamplification is always available to cause limiter 185 to performproperly, and to further suppress some signals which are not ofsufiicient magnitude to give a clean speed indication and to take careof slight decreases in signal amplitude which may cause the frequencycounter 185, to which the limiter output is connected, to lose itscount, a clamping circuit is provided, which comprises a clamp amplifier187 and clamp 188, and connected to the limiter 185 input to shunt apart of the signal output of amplifier 184 when clamped, as by a voltagedivider circuit for example, not shown herein. The clamp is controlledby the clamp amplifier 187 from the limiter 185, so that when suliicientsignal has been received by the limiter-amplifier circuit 185, whenclamped, to provide a clean speed reading, if unclamped, the clampaction of the clamping circuit responds, to decrease the shunting elfectof the clamp on this signal output of amplifier 184 and thus toautomatically increase the signal input to the limiter-amplifier 185,and thus the circuit becomes unclamped.

This same clamp and clamp amplifier circuit, after the target haspassed, again reduces the gain of the amplifier automatically until suchtime as another target produces a signal of sufficient magnitude to givea clean speed reading.

The speed pulse signals from limiter-amplifier 185 are fed to afrequency counter 186 which produces an output voltage varying linearlywith the frequency of the speed signal fed into it. The linear outputvoltage, indicative of the speed of the moving vehicle, is thenamplified by output amplifier 139. The output of the latter is suppliedto a meter indicator 182 which measures the speed directly in miles-perhour and to a speed recorder 18?) for graphically storing the speedinformation. In the case of the corresponding speed translator 181 ofFIG. 7 the output as supplied to meter indicator 132; and speed recorder183 at the monitor station.

It will be noted that in FIG. 4b certain elements are shown to provideoutputs to a low speed alarm and high speed alarm, these elementscomprising the take-off line 250 feeding the speed signal at the limiter185 input also to the low-pass filter 251 and high-pass filters 253. Theoutput of the low-pass filter is fed to amplifier ll detector 252 toprovide at output 25s a relay operating voltage indicating excessivelylow speed, as determined by the low frequency pass of the filter whichmay be adjustable.

Similarly the high pass filter 2.53 supplies its output to amplifierdetector 254 to provide another relay operating voltage at its output257 to indicate excessively high speed as determined by filter 253 whichalso may be adjustable. These outputs 256 and 257 control alarm relayssuch as shown in FIG. 2a, for example, the low speed relay LRparticularly being of a slow acting type to avoid response to anytransitory low frequency signal from the cosine effect as a high speedvehicle passes through a side part of the radio energy beam for example,at a maximum angle to the beam BEE-8E2.

These elements 25% through 257 are shown for con venience in FIG. 4b butwould ordinarily be provided, when the low speed or high speed alarmfeatures are desired, only at the remote monitor station, where thetraflic supervisory personnel would be located for observation of thetraffic conditions indicated or recorded. Thus these elements 25tl-257would ordinarily be provided, when such alarm features are desired, onlyin the speed translator 1%1 at the monitor station '70 or 2 30 and notin the speed translator 181 at the sampling station.

It will be obvious that the low speed alarm or high speed alarm might beomitted if desired, along with the associated elements in the 25tl257group.

The above substantially shows how supervision or surveillance of trafficconditions at a particular sampling area along a given highway facilityis obtained and maintained. However, Where a considerable expanse ofhighway facility is to be covered there must of necessity be a largernumber of trafiic sampling points or stations to properly monitor thetraffic situation thereat.

FIG. 2 shows a typical dual twin-lane highway facility with a central orseparation strip island between eastbound and westbound trafiic asindicated by the directional arrows E and W respectively, with a seriesof spaced sampling stations along each twin-lane roadway, i.e. the eastand west drives, on lanes CE and DE and lanes AW and BW respectively, toobtain at the particular sampling location traflic information as tospeed and volume. The information is then relayed, from each of thespaced sampling stations, to a remote central monitoring station Ztltl.

FIG. 2 illustrates a simplified arrangement by which speed informationfor example from the several sampling stations may be transmitteddirectly to corresponding monitor indicators and associated recorders atthe central monitoring station. When speed information alone is to betransmitted and indicated, the composite mixer 24 and associatedresolver 71 of FIG. 1 may be omitted and the speed signal transmitteddirectly from the speed sensing detector Ell at 23a of FIG. 4a to thecorresponding monitor indicator of FIG. 2 which may include the speedtranslator 131 of the type illustrated by translator 181' of FIG. 4b,along with the speed indicator 182 of FIG. 1 and FIG. 7. The recorderwhen included may correspond with recorder 183 of FIG. 1 and FIG. 7.

Thus in FIG. 2 for each sampling station traffic detector there is acorresponding monitor indicator and its associated recorder at thecentral monitoring station, and from one central point, traflicconditions from a plurality of sampling points may be properly observedand recorded and appropriate steps taken to correct any abnormalitywhich may develop either immediately, due to some accident, or over aprolonged period of time. In the preferred form of the central monitorstation, there is further provided at each of the monitors for mountingat each representative monitor an alarm indicator mechanism for settinginto operation an alarm to indicate when the traffic volume and/ orspeed of moving vehicles at or along l2 a particular sampling stationeither exceeds or falls below certain predetermined levels.

As illustrated in FIG. 2, the representative monitor indicators are eachprovided with indicator lights (L) (H) to indicate that the speed orvolume is low or high, or below a predetermined level or above anotherpredetermined level respectively. Therefore, for example, if the trafiicspeed at sampling station 15 falls below the preselected level, thelight L on monitor indicator will e illuminated and a common alarm bell212 will ring to indicate such abnormality. The alarm circuits areprovided with a release pushbutton or switch PB associated with eachmonitor indicator for resetting the alarm, and shown between the L and Hlamps.

common bell. or buzzer alarm gives the supervisory per? nel a warningthat something at one of the sampling stations is amiss, and one or moreof the indicator lights (is) or (H) on the monitor indicators will glowto show which of the sampling stations, and therefore the location,where the particular abnormal condition exists.

A 24 our clock and date indicator is also shown in the centralmonitoring station adiacent the monitor indicators f example, along witha place designated NOTES for writing notations of data for photographicrecording purposes if desired.

FIG. 2a shows one form of alarm circuit arrangement, for the alarm belland loW and high indicator lights L and H of FIG. 2. Only two sets ofcircuits are shown for the IE and 25' monitor indicators respectively,since these circuits are representative of all, each circuit having alow level alarm relay LR and a high level alarm relay HR for operatingthe respective lamps L and R associated with its wn monitor indicator,and also for operating the common bell or buzzer alarm 212. It will benoted that the bell operating circuit extends to the several lowercontacts of the several LR and HR relays in parallel, with extensionsfor connections to corresponding relay contacts for the 1W, 2W, 3v and35, etc. monitor indicators so that operation of any relay will alsooperate the common bell.

Considering the alarm circuit for 113 more fully as representative thelow and high speed operating voltage inputs 231 and for example enter atthe left and right at the foot of the figure from the associated speedtranslator low speed and big 2 speed outputs 2.56 and 257 respectively,and extend to the LR and HR relay coils respectively in parallel withthe associated lamp, L for LR and H for HR, the upper sides of the lampsbeing returned to the negative power terminal or ground. The other sidesof the coils of relays LR and HR extend to such negative power terminalvia a normall closed pushbutton or switch common to the associated pairof relays LR and HR for 1E. The upper contacts of these relays providelockin or holdin circuits for the relay and associated lamp, so that theparticular relay once energized by incoming operating voltage (positive)on its input line, will remain energized over its upper contact alongwith its lamp and will also energize the common bell, until the releaseswitch PE is opened manually for example by the observer, upon which theparticular relay lamp and common hell are all released.

Where the alarm circuitry of FIG. 2a or additional similar alarmcircuitry is employed for low and traffic volume the input circuits maybe connected with output circuits of volume level classifier of FIG. 8b,such as 1 .4% for low and lid-b" for high for example.

It can be appreciated that the central monitoring station may not need amonitor indicator corresponding to each of the sampling stations.Rather, as shown in Fl. 3, a central monitoring station 214- may beprovided with a selective switching system whereby only a limited numberof representative monitors 2.15, 216 and 2.17 and an equal or fewernumber of recorders 213 and 219 are in stalled. By the appropriatesetting of the selector switches 2.20, 221 and 222 a particular monitormay be selected to function with a particular sampling station. Also bythe appropriate setting of each of the recorder selector switches 13 223and 224, a recorder may be selected to function with a particularmonitor.

Although FIG. 2 shows a simplified arrangement for centralizedmonitoring of a number of individual sampling stations along a highwayfacility particularly for speed information, it will be understood thatit also serves diagrammatically to illustrate such centralizedmonitoring of volume information, or speed and volume informationtogether, from the several spaced sampling stations. It is obvious thata plurality of sampling stations and associated remote monitor stationsof the type shown in FIG. 1 in block form, and in FIGS. 4a-4b, 5a5b,PEG. 7 and FIG. 8a-8b in more detailed form, may be arranged withclosely adjacent monitor indicators, and with alarm features as desiredin the general form of FIG. 2, with monitor indicators including bothspeed and volume indications. Similarly the recorders of the centralmonitoring station 2% of FIG. 2 may be dual or doubled for recordingboth speed and volume.

For obtaining speed and volume information the blocks indicated asTRAFFIC SPEED DETECTOR in FIG. 2 would include trafiic speed and volumedetectors, and may transmit the outputs directly over individualchannels or by means of the composite mixer and resolver feature as inthe preferred form.

It will be understood that in some instances the volume meter 175 ofFIG. 8b and/or recorder 92 may be included in the central station 290,without the volume level classification feature of FIG. 812, but wherethe output circuits of the latter are desired for control of high andlow alarm circuits as volume alarms, this volume level classificationfeature would be included to permit the low and high volume alarms to beoperated by output circuits 149 and 145 respectively for example.

As a further alternate arrangement some of the sampling stations andremote monitors of FIG. 2 might give speed alone and others volumealone, either by alternating adjacent spaced sampling stations orotherwise.

It will also be understood that the spacing between the spaced samplingstations may be uniform in some installations, or may be varied in otherinstallations in accordance with the characteristics of the differentsections of the highway facility. Thus in sections of more than twolanes in each direction or having shorter range of visibility or otherphysical or expected heavy or generally slower trafic conditions thesampling stations might be more closely spaced than on more open orstraight or generally lighter trafi'ic or normally higher speedsections, for example. Such spacing may vary from somewhat less than onemile to a number of miles, depending on the degree of coverage desired,for example. The sampling station locations might in some instances berelated to entrances and exits or traflic interchanges on the highwayfacility.

Although the invention has been described and illustrated in severalaspects of remote traffic supervision and in a preferred form havingboth indicating and recording and also having alarm circuits for highand low traffic conditions, it will be appreciated that under somecircumstances sub-combinations of features such as by indicating withoutrecording, or by recording without separate indicating, or by recordingor indicating without classification into several volume levels willhave individual value, as may also the remote centralized monitoring ofspeed alone at appropriately spaced stations. In the latter connectionit will be appreciated that one stationary sampling station samples thespeed of more traffic units than a patrol oflicer on mobile patrolmoving with the traflic, and that sampling at spaced points of knowndistance and approximate travel time at any particular speed togetherwith providing the traffic speed information at closely adjacent andidentified points as on a panel at the centralized monitor station,enables comparison of conditions at the spaced points by the 14 trafficsupervisory authority, quickly and as continuously as desired.

The volume sensing detectors 1 and 2 of FIG. 1 may for example, be ofthe type disclosed in the Manual for Model RD-1 and RD-lA Radar VehicleDetector copyright 1956 by Eastern Industries, Inc., which is thesubject of a copending application by me.

The remote or centralized monitoring station may be at police patrolheadquarters or other trafiic supervisory location where. radiocommunication may be had with mobile patrol for example.

Several aspects and forms of the invention have been pointed out aboveand illustrated in the drawings, and it will also be appreciated thatvarious further modifications or rearrangements of the illustrated ordescribed embodiments of the invention or in parts thereof may be madewithout departing from the spirit of the invention within the scope ofthe appended claims.

I claim: I

1. A tratfic surveillance system for surveying vehicular traflic speedand volume conditions over a highway facility and comprising a trafiicsampling station having vehicular speed and passage detection apparatusfor producing electrical signals indicative of the speed and passage ofmoving vehicles, means for combining the speed and passage signals toproduce a composite electrical signal, said combining means includingmake-before-break relay circuit means activated responsive to the saidpassage sensing detection apparatus output signals, oscillation meansoperably responsive to the activated relay means for producing anoscillatory signal output, and output circuit means for receiving theoscillatory signal indicative of the traflic passage and the speedsignal indicative of the vehicle speed and producing therefrom theoutput composite electrical signal, means for transmitting the compositeelectrical signal along a pre-determined transmission path,

a remote sampling station monitor for receiving the transmittedcomposite electrical signal and comprising a signal resolver forreceiving and resolving the composite signal into the tralfic passageelectrical signals and speed electrical signals,

means for receiving the speed electrical signals and producing a voltagetherefrom proportional to the speed of the moving verncles, meansresponsive to said voltage for producing a visual speed indication,

means for receiving the passage electrical signals and producing afurther voltage therefrom proportional to the .trafiic volume level ofthe moving vehicles,

and means responsive to said further voltage for producing a visualtrafiic volume level indication.

2. A trafiic surveillance system according to claim 1 and wherein thesaid oscillation means includes a relaxation oscillator having anelectron tube control electrode biasing means operably responsive to theactuation of the make-before-break relay means and causing theoscillator to generate oscillations in accordance with the saidactuations, and the output circuit means includes an amplifier having apair of input stages and an output stage and whereby the saidoscillations are fed to one of the input stages and the speed signal isfed to the other input stage, the said signals appearing at the outputstage as a composite signal.

3. A traffic surveillance system according to claim 2 and wherein thesaid control electrode biasing means of the relaxation oscillatorincludes a chargeable capacitor charged through the said controlelectrode to maintain the oscillator non-conductive by virtue of thebias thereon and adapted to be discharged by the relay means when thesaid relay means is actuated and thereby removing the bias and causingthe oscillator to conduct.

4. A traffic surveillance system for surveying vehicular trafiic speedand volume conditions over a highway facility and comprising a trafiicsampling station having vehicular speed and passage detection apparatusfor producing electrical signals indicative of the speed and passage ofmoving vehicles,

means for combining the speed and passage signals to produce a compositeelectrical signal,

means for transmitting the composite electrical signal along apre-determined transmission path,

a remote sampling station monitor for receiving the transmittedcomposite electrical signal and comprising a signal resolver forreceiving and resolving the composite signal into the traffic passageelectrical signals and speed electrical signals, said resolvercomprising an input circuit for receiving a composite signal consistingof vehicular trafiic passage and speed indicative signals and a pair ofoutput circuit means for separating the passage and speed signals andincluding a low pass filter circuit for discriminating against allfrequencies above a preselected cut-off frequency and a tuned circuittuned to a pre-selected fixed frequency outside the low pass filter passband, the low pass filter substantially passing all indicative speedsignal frequencies and the tuned fixed frequency circuit passing onlythe indicative passage signal frequency, means for receiving the speedelectrical signals and producing a voltage therefrom proportional to thespeed of the moving vehicles,

means responsive to said voltage for producing a visual speedindication,

means for receiving the passage electrical signals and producing afurther voltage therefrom proportional to the trafiic volume level ofthe moving vehicles,

and means responsive to said further voltage for producing a visufltraific volume level indication.

5. A traffic surveillance system according to claim 4, and wherein oneof the output circuit means includes signal detection means adapted toreceive the vehicular trafiic passage signals and produce an outputpassage signal pulse therefrom and relay means including a normallyinoperable output circuit amplitude responsive to the reception of theoutput passage signal pulse to effect the operation of the outputcircuit.

6. A trafiic surveillance system for surveying vehicular tratfic speedand volume conditions over a highway facility and comprising a traificsampling station having vehicular speed and passage detection apparatusfor producing electrical signals indicative of the speed and passage ofmoving vehicles,

means for combining the speed and passage signals to produce a compositeelectrical signal,

means for transmitting the composite electrical signal along apre-determined transmission path,

i=5 a remote sampling station monitor for receiving the transmittedcomposite electrical signal and comprising a signal resolver forreceiving and resolving the composite signal into the traflic passageelectrical signals and speed electrical signals, means for receiving thespeed electrical signals and producing a voltage therefrom proportionalto the speed of the moving vehicles, means responsive to said voltagefor producing a visual speed indication, means for receiving the passageelectrical signals and producing a further voltage therefromproportional to the trafiic volume level of the moving vehicles, andmeans responsive to said further voltage for producing a visual trafiicvolume level indication, the said volume level indicator means includinga plurality of volume range switching means each having an outputcircuit associated therewith and each of said plurality of volume levelrange switching means responsive to a different signal amplitude leveltherefor indicative of the vehicular traffic volume level overpre-selected traffic volume ranges, each of said output circuitsindividually operable in response to the operation of its associatedvolume level range switching means, and means connecting said outputcircuits for selectively providing a single output at only one of saidoutput circuits in response to different selective signal amplitudes.

7. A system according to claim 6, and wherein the volume level rangeswitching means includes switching electron discharge devices normallynonconductive and each having an input and an output circuit meanstherefor, each of said input circuit means individually responsive to adifferent signal amplitude level indicative of the vehicular trafiicvolume level over preselected traffic volume level ranges causing theelectron discharge device to conduct to produce in the output circuitmeans indicative volume level signals over the pre-selected volume levelranges.

8. A system according to claim 7 and wherein the output circuit meanscomprises a relay operably responsive to the conduction of the dischargedevice and output terminal means for receiving volume level signals inresponse to the operation of the relay, and the input circuit meanscomprises a pair of selective networks one adapted to cause the rapidconduction of the discharge device in response to the energization ofthe relay and the other adapted to cause rapid cut-off of the dischargedevice in response to the de-energization of the relay to effect rapidvolume level range switching from one traffic volume level range to anadjacent traffic volume level range.

References Cited by the Examiner UNITED STATES PATENTS 2,150,776 3/39Moles 34031 2,165,800 7/39 Koch 343117 X 2,181,728 11/39 Greentree340263 2,477,567 8/49 Barker 34022 2,640,973 6/53 Cleaver 340-1822,659,014 11/53 Scherbatskoy 340-182 2,817,081 12/57 Van Roberts 34392,999,999 9/61 Bartelink 3438 CHESTER L. JUSTUS, Primary Examiner.

FREDERICK M. ST RADER, Examiner.

1. TRAFFIC SURVEILLANCE SYSTEM FOR SERVEYING VEHICULAR TRAFFICE SPEEDAND VOLUME CONDITIONS OVER A HIGHWAY FACILITY AND COMPRISING A TRAFFICESAMPLING STATION HAVING VEHICULAR SPEED AND PASSAGE DETECTION APPARATUSFOR PRODUCING ELECTRICAL SIGNALS INDICATIVE OF THE SPEED AND PASSAGE OFMOVING VEHICLES, MEANS FOR COMBINING THE SPEED AND PASSAGE SIGNALS TOPRODUCE A COMPOSITE ELECTRICAL SIGNAL, SAID COMBINING MEANS INCLUDINGMAKE-BEFORE-BREAK RELAY CIRCUIT MEANS ACTIVIATED RESPONSIVE TO THE SAIDPASSAGE SENSING DETECTION APPARATUS OUTPUT SIGNALS, OSCILLATION MEANSOPERABLY RESPONSIVE TO THE ACTIVATED RELAY MEANS FOR PRODUCING ANOSCILLATORY SIGNAL OUTPUT, AND OUTPUT CIRCUIT MEANS FOR RECEIVING THEOSCILLATORY SIGNAL INDICATIVE OF THE TRAFFIC PASSAGE AND THE SPEEDSIGNAL INDICATIVE OF THE VEHICLE SPEED AND PRODUCING THEREFROM THEOUTPUT COMPOSITE ELECTRICAL SIGNAL, MEANS FOR TRASMITTING THE COMPOSITEELECTRICAL SIGNAL ALONG A PRE-DETERMINED TRANSMISSION PATH, A REMOTESAMPLINGSTATION MONITOR FOR RECEIVING THE TRANSMITTED COMPOISTEELECTRICAL SIGNAL AND COMPRISING A SIGNAL RESOLVER FOR RECEIVING ANDRESOLVING THE COMPOSITE SIGNAL INTO THE TRAFFICE PASSAGE ELECTRICALSIGNALS AND SPEED ELECTRICAL SIGNALS,